feat: start parser

Cargo.lock

@@ -2,6 +2,12 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "anyhow"
+version = "1.0.57"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "08f9b8508dccb7687a1d6c4ce66b2b0ecef467c94667de27d8d7fe1f8d2a9cdc"
+
 [[package]]
 name = "atty"
 version = "0.2.14"
@@ -25,6 +31,12 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
+[[package]]
+name = "bytes"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c4872d67bab6358e59559027aa3b9157c53d9358c51423c17554809a8858e0f8"
+
 [[package]]
 name = "clap"
 version = "3.1.14"
@@ -64,6 +76,16 @@ dependencies = [
  "os_str_bytes",
 ]
 
+[[package]]
+name = "combine"
+version = "4.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2a604e93b79d1808327a6fca85a6f2d69de66461e7620f5a4cbf5fb4d1d7c948"
+dependencies = [
+ "bytes",
+ "memchr",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.11.2"
@@ -107,11 +129,19 @@ version = "0.2.125"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5916d2ae698f6de9bfb891ad7a8d65c09d232dc58cc4ac433c7da3b2fd84bc2b"
 
+[[package]]
+name = "memchr"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+
 [[package]]
 name = "neptune"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "clap",
+ "combine",
 ]
 
 [[package]]

Cargo.toml

@@ -6,4 +6,6 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+anyhow = "1.0.57"
 clap = { version = "3.1.14", features = ["derive"] }
+combine = "4.6.4"

src/ast.rs

@@ -1,8 +1,10 @@
+#[derive(Debug)]
 pub struct Program<'a> {
     pub version: String,
-    pub term: &'a Term<'a>,
+    pub term: Term<'a>,
 }
 
+#[derive(Debug)]
 pub enum Term<'a> {
     // tag: 0
     Var(String),
@@ -28,6 +30,7 @@ pub enum Term<'a> {
     // Builtin
 }
 
+#[derive(Debug)]
 pub enum Constant {
     // TODO: figure out the right size for this
     // tag: 0

src/lib.rs

@@ -1,2 +1,3 @@
 pub mod ast;
 pub mod cli;
+pub mod parser;

src/main.rs

@@ -1,7 +1,14 @@
 use neptune::cli::Cli;
+use neptune::parser;
 
-fn main() {
+fn main() -> anyhow::Result<()> {
     let args = Cli::default();
 
-    println!("loading {}", args.input.display());
+    let code = std::fs::read_to_string(&args.input)?;
+
+    let program = parser::program(&code)?;
+
+    println!("{:#?}", program);
+
+    Ok(())
 }

src/parser.rs

@@ -0,0 +1,63 @@
+use combine::{
+    between,
+    parser::char::{digit, spaces, string},
+    sep_by, token, ParseError, Parser, Stream,
+};
+
+use crate::ast::{Program, Term};
+
+pub fn program(src: &str) -> anyhow::Result<Program> {
+    let mut parser = program_();
+    let result = parser.parse(src);
+
+    match result {
+        Ok((program, _)) => Ok(program),
+        Err(err) => Err(anyhow::anyhow!("{}", err)),
+    }
+}
+
+pub fn program_<'a, Input>() -> impl Parser<Input, Output = Program<'a>>
+where
+    Input: Stream<Token = char>,
+    Input::Error: ParseError<Input::Token, Input::Range, Input::Position>,
+{
+    let prog = string("program")
+        .with(spaces())
+        .with((version(), spaces(), term()).map(|(version, _, term)| Program { version, term }));
+
+    between(token('('), token(')'), prog).skip(spaces())
+}
+
+pub fn version<Input>() -> impl Parser<Input, Output = String>
+where
+    Input: Stream<Token = char>,
+    Input::Error: ParseError<Input::Token, Input::Range, Input::Position>,
+{
+    sep_by(digit(), token('.'))
+}
+
+pub fn term<'a, Input>() -> impl Parser<Input, Output = Term<'a>>
+where
+    Input: Stream<Token = char>,
+    Input::Error: ParseError<Input::Token, Input::Range, Input::Position>,
+{
+    string("var").map(|x| Term::Var(x.to_string()))
+}
+
+#[cfg(test)]
+mod test {
+    use combine::Parser;
+
+    const CODE: &str = include_str!("../example/plutus-core");
+
+    #[test]
+    fn parse_program() {
+        let result = super::program_().parse(CODE);
+
+        assert!(result.is_ok());
+
+        let program = result.unwrap().0;
+
+        assert_eq!(program.version, "1.0.0");
+    }
+}